Extrusion die construction



June 12, 1962 H. .1. IMMOHR EXTRUSION DIE CONSTRUCTION 2 Sheets-Sheet 1 Filed Jan. 12, 1960 FIG. 2

MATERIAL INVENTOR PELLETS HARRY J IMMOHR 139/ ATTORNEY June 12, 1962 Filed Jan. 12, 1960 H. J. IMMOHR EXTRUSION DIE CONSTRUCTION FIG. 3-4

INVENTOR HARRY J. IMMOHR ATTORN Y 2 Sheets-Sheet 2 EXTRUSION DEE CONSTRUCTION Harry Johannes lrnrnohr, H. lirnrnohr Machines, New Milford, Pa.

Filed .lan. 12, 196i), Ser. No. 1,990 9 Claims. (Cl. 107-14) This invention relates to improvements in extrusion die construction, and more particularly to an improved extrusion die construction for use in pelleting materials such as livestock and poultry feeds.

The rapidly increased use of pelleted feeds (amounting to approximately sixty percent of the forty million tons of feed produced in 1958) has resulted in greater and greater demands, in terms of higher production rates and increased die life, being made on pellet producing equip ment, and in turn in studies being directed toward the solution of the problem of a pitting type of corrosion of pellet die-hole surfaces, leading to reduced production rates and shortened die life, which has arisen in recent years. As reported in an article entitled, Extending Die Life, by R. L. Patterson et al., The Procter-Gamble Company, Cincinnati, Ohio, Proceedings of the 1959 Feed Production School, Kansas City, Missouri, entitled Pelletting, such corrosion or pitting, while at first considered to be somehow associated with the use of fat in the formulation of the feeds undergoing pellcting, both for its nutritional value and also for increased production and lower power requirements in pelleting, is more probably due to electrochemical (electrolytic) action occurring at surface imperfections along the die holes which appears to be caused by unduly high levels of moisture content.

As a solution for this problem and on the basis of studies made for report purposes, the aforesaid article suggests improved diesurface finish obtained, for example, by a high polish applied to the die-hole surfaces through the use of better abrasives, or by plating the die-hole surfaces with a durable metal plating or coating passive to the deleterious electrolytic action, ire. nickel, or im proved die alloys for the rings or plates in which the dieholes are formed. While acknowledging that the aforesaid suggestions may be and probably are. feasible if die manufacturing and maintenance costs are not a consideraticn, the fact of the matter is, however, that the cost of applying a high polish or a nickel plating to the diehole surfaces of a die plate or ring having, according to standard practice, a minimum of 2,200 and a maximum of 6,600 holes, and the material and labor costs of drilling a die plate or ring made of stainless or high nickel alloys with such a large number of finished holes, is so great as to rule out these suggestions as providing a practical solution of the problem. Obviously, mere replacement of a worn die made of ordinary die metal with one costing many times more than the original die and which must also be bodily replaced when worn is no answer to the problem when the latter is considered from the cost angle.

While from other sources, no doubt prompted by the use of die inserts in metal and plastic extrusion dies, has come the further suggestion of using die-hole inserts in pelleting dies (see, for example, patents to Meakin No. 2,759,219, dated October 11, 1956, and No. 2,902,949, dated September 8, 1959), such on the present evidence have not provided the solution because the resulting die construction is again so unduly complicated and expensive that it fails to meet the firstand maintenance-cost limitations of the pelleted feeds industry. Thus, it can be said that while the aforesaid patents recognize the problem, the solutions which they offer are unsatisfactory.

Stated broadly, an object of the present invention is the provision of an extrusion die construction for use in feed pelleting mills, which provides an effective and dependable solution of the problem of deterioration or pitnited States Patent ting of the die-hole surfaces thereof due to electrolytic action of the feeds being pelleted thereon and which at the same time is inexpensive and practical and in accordance with sound die'making principles.

Another object of the invention is the provision of a feed-pelleting die having die-hole surfaces constructed and arranged as to give the advantages of a highly polished and/or high alloy-coated surface and the like as insures long die life and high production rates, yet which can be manufactured at a cost no greater and possibly less than pelleting dies of the prior designs.

A further object of the invention is the provision of a feed-pelleting die having the aforesaid advantages yet whose construction and arrangement is such as to facilitate reconditioning of the die if and when needed.

Still another object of the invention is the provision of an improved pelleting die using inserted die-hole surfaces, for convenience hereinafter referred to as die insorts, and which is characterized by simple, thoroughly dependable construction, as well as a good die design.

Yet another object of the invention is the provision of an improved method of constructing pelleting dies which imparts t0 the die-ho1e surfaces thereof the properties of effectively resisting the pitting type of corrosion found to occur in prior pelleting dies using ordinary die metals.

The above and additional objects and features of advantage of the invention will appear from the following detailed description, taken with the accompanying drawings illustrating a preferred embodiment, as well as a method of constructing the pelleting die according to the invention, wherein FIG. 1 is a part-sectional, broken-away perspective view illustrating a die plate or ring constructed according to the principles of the present invention;

PEG. 2 is an enlarged side elevation, partly in section, illustrating an improved die according to the invention in operation; and

FIGS. 3A-3D, inclusive, are diagrammatic views illustrating a preferred manner of fabricating the die- 101$ inserts and thereupon of assembling same in the holes of the die ring or plate according to the invention.

Referring to the drawings in detail, reference numeral 16) designates a die member in the form of a die ring but which may also be a flat plate, which is provided with a multiplicity of die holes 12 extending from inner to outer faces of said ring. As is well known, said die holes constitute extrusion passages for the material being pelleted, which latter is forced through said holes by a mill roll 14 (or equivalent) rolling on the inner face of the die ring.

The aforesaid die holes 12 are drilled in the conventional manner, and it is a feature of the invention that said holes may be coarse-drilled, with no emphasis required to be placed on finishing of the holes during drilling or by subsequent reaming. The die holes further have larger diameter at their outer ends than at their inner ends 12a and such increase in outer-end diameter may be effected by counter-boring said die holes from the outer side or face of the die member inwardly to a predetermined distance short of the inner face of said die member, the inner ends of the so-formed counter-bores 16 terminating at their inner ends in abrupt shoulders 13.

As illustrative of the constructional details of the pelleting die so far described, the thickness of the die ring 10 may be of the order of 1%"; it is drilled with 2,200-6,600 die holes 12 of approx.) diameter; and the counter-bores 16 are drilled to a depth such that they terminate from the inner or millroll side of the die ring 10. The diameter enlargement of each die hole provided by the counter-bores is preferably such as to enable insertion therein of a sleeve-form insert, to be later .described in detail, having .020 wall thickness (approx) without at the same time disturbing the continuity of the extrusion passages as determined by the diameter thereof at the compression or inner ends 12a of said passages. It is of course to be understood that while the aforesaid dimensions are in accordance with standard practice and good pellet-rnill design, applicant is not to be bound thereby, inasmuch as some variation in thickness of die ring, diameter of the die passages, etc., may be found necessary for a particular application or a particular type of the material being pelleted or variations in length and diameter of the pellets.

According to the invention, the aforesaid sleeve-form inserts, which are generally designated 29 in FIGS. 1 and 2, are made of a material resistant to the pitting-type of corrosion found to effect die-hole surfaces of die members made of the usual die metals and which has recently created a serious problem in the pelleting mill art. Among such materials may be mentioned stainless stee brass, the ceramics, cemented carbide and the like, all of which are characterized by passivity to the aforesaid corrosive effects and/ or by a hard and high surface polish not likely to containsur-face imperfections. While such sleeves, when fashioned from metal, i.e. stainless steel, may comprise short lengths of seamless drawn tubing of the proper diameter and gauge as to fit the counter-bores and at the same time not destroy the continuity of the die passages as determined by their ,5 compression-end diameter, and may be secured within the counterbores in various ways, for example, by brazing, welding, riveting, etc., a method of forming the tubular or sleeve-form insorts and of assembling and securing them in place within the diehole counter-bores which is preferred because of its simplicity and low cost will now be described in connection with FIGS. 3A-3D, inclusive.

Referring to FIG. 3A, such is illustrative of piece Zia of insert stock which has preferably been cut from a long strip thereof, the cut piece having length slightly less than the axial length of the die-hole counter-bores i6 and width such that, when edge-rolled to a split-sleeve formation according to FIG. 3, the resulting sleeve will have outer and inner diameters slightly oversize with respect to the diameters of the counter-bores 16 and of the inner, i.e. the non-counterbored ends, of the die passages, respectively. FIG. 3b illustrates the insert Ztla partially rolled to split-sleeve formation, with FIG. 3C illustrating the fully rolled insert completed and ready for assembly in the counter-bores of the die plate. It is to be noted that because of its split-sleeve construction, the completed insert 20b shown in FIG. 3C is contractible and hence capable, when contracted, of exerting a radially outward force.

Referring now to FIG. 3D, such shows (leftmost die hole) the split-sleeve insert 20b according to FIG. 3 being assembled in its counter-bore 16 of a die ring it}, and it will be understood that such can be effected simply by pressing the insert axially into the counter-bore until it engages tight against the shoulder 18. Such assumes proper dimensioning of the sleeve insert so that, when pressed into its counter-bore as aforesaid, it is contracted until its longitudinally extending split edges come together to form a closed seam and thereupon it exerts radially outward pressure on the peripheral counter-bore wall consequent to its tendency to return to unstressed condition. It is also to be understood that the dimensioning of the sleeve-form insert is such that when compressed in its counter-bore as aforesaid, its inner diameter does not exceed the diameter of the inner or compression ends 14 of the die passages, with the result that when finally assembled in their counter-bores, the inserts preserve the continuity of the extrusion passages.

While as above suggested the inserts following their assembly in the die-ring counter-bores as aforesaid may be secured in place in numerous ways, a very simple form of securement (additional to that of their frictional hold- 5 plained, by providing said inserts with somewhat shorter length than the axial length of said counter-bores. A tool for performing this peening-over or upsetting operation is indicated at St in FIG. 3D, but it is to be understood that such is suggestive only of various forms of tools which may be used with good effect. But, regardless of the maner in which the die-hole inserts 20 are secured in place at their outer ends, it is highly desirable that the form of securement ultimately selected be one which can be readily broken open when and if it should become necessary to 15 recondition the die by removal of worn inserts and replacement thereof with new inserts.

The above description makes it plain that the sleeveform inserts 20, rather than extending completely or approximately to the inner ends of the die passages, terminate about /8" from said inner ends. In explanation,

not only the studies of pelleting die life reported in the above-mentioned Feed Production School Pelleting publication but other sources as Well have demonstrated that the objectionable pitting or corrosion effects are negligible at the inner or compression end of the die passages for about from the inner die face outwardly. Therefore, there appears to be no need for continuing the sleeve-form inserts inwardly to the inner or mill-roll face of the die ring. Moreover, the termination of the inserts short of the inner face of the die ring, taken with the setting back of the inserts in the counter-bores, is of advantage in that it supplies a convenient stop shoulder 18 which is utilized in accurately locating the inserts upon their assembly with the die ring in their proper final position.

Without further analysis, it will be appreciated that the above described die construction for use in pelleting dies satisfies the objectives of the invention as explained in the foregoing. More particularly, the invention provides an extrusion die construction for use in pelleting livestock and poultry feeds which overcomes the disadvantages in terms of short die life and reduced production rates which quite recently has created a problem in the use of dies of the prior design, due to their die surfaces being affected by a pitting-type of corrosion, probably due to the electrolytic action thereon caused by the moisture content of the hydrolyzed fats. The die insert construction of the invention is also noteworthy because of its overall cheapness and effectiveness, and also because it permits die reconditioning with the minimum of labor costs.

So, too, the invention provides a simple yet effective method of pelleting die construction which enables the production of long-life and high production-rate dies at a cost not greater than that of manufacturing the conven- 'tional die, and also it results in the production of a die which can be very simply reconditioned if and when such becomes necessary.

As many changes could be made in carrying out the above constructions without departing from the scope of the invention, it is intended that all matter contained in 0 member inwardly toward but terminating in an abrupt shoulder located a predetermined distance short of said inner face which substantially equals the length of the die hole measured from the inner compression end there of which in the die made of the usual die metal is generally free of the objectionable pitting-type of corrosion caused by the electrolytic action of the feed materials being pelleted thereon, and a die hole insert in each of said counter-bores in abutting rciation to the shoulder thereof and having an inner diameter corresponding substantially to that of the die hole inwardly of said shoulder, said insert comprising a sleeve fashioned from thin sheet material which is resistant to the aforesaid objectionable pitting-type of corrosion and being press-iitted in its counter-bore to a degree enabling it to frictionally secure itself therein, and means at the outer end of each of the counter-bores and being effective on the outer end of its sleeve for securing said sleeve against unintentional axial removal from said counter-bore.

2. Pelleting die construction substantially as set forth in claim 1, wherein each said insert is slightly shorter than said counter-bore and is held in place in its counterbore, at least in part, by the material of the die member extending along the outer end of the sleeve.

3. Pelleting die construction substantially as set forth in claim 1, wherein each said insert comprises a strip of said thin sheet material edge-rolled to split-sleeve formation and has an outer diameter initially slightly greater than than of said counter-bore, whereby, when said insert is pressed into the counter-bore, it is slightly contracted as results in a tendency to expand to its unstressed diameter and, in so doing, to frictionally secure itself to said counter-bore wall surface.

4. Pelleting die construction substantially as set forth in claim 3, wherein said insert is slightly shorter than its associated counter-bore and the material of the die member extending along the outer edge of the sleeve is upset so as to extend over said end, thereby additionally securing the insert in place within its counter-bore.

5. Pelleting die construction substantially as set forth in claim 1, wherein each said insert comprises a narrowwidth strip of said material edge-rolled to split-sleeve formation and being initially slightly oversize with respect to the diameter of the counter-bores, the construction and arrangement being such that said split-sleeve insert is contracted in its assembly in its counter-bore to an outside diameter corresponding to the diameter of its counter-bore and to an inside diameter not exceeding that of the non-counterbored inner end of the die hole.

6. Pelleting die construction substantially as set forth in claim 1, wherein each said insert has the form of a longitudinally split-sleeve which is initially oversize with respect to its counter-bore but upon insertion being in a state of contraction whereby it frictionally secures itself to the wall of its counterbore.

7. Pelleting die construction substantially as set forth in claim 6, plus additional insert-securing: means operative on the outer end of each insert.

8. The method of pelleting die construction comprising: providing a die member with a multiplicity of initially uniform-diameter die holes constituting extrusion passages which extend through said die member from its inner to its outer face, counter-boring said die holes from their outer ends inwardly to a predetermined distance short of the inner face of the die member which substantially equals the length of the die hole measured from the inner compression end thereof which in pelleting dies made of the usual die metal is generally free from the electrolytic action thereon of the material being pelleted and in such manner as to form an abrupt shoulder at the inner end of the so-formed counter-bores, providing a multiplicity of sleeve-form inserts, one for each hole, of a thin sheet material which is passive to the aforesaid electrolytic action thereon of the material being pelleted and having outer and internal diameters corresponding substantially to the diameters of said counter-bores and the inner non-counterbored ends of the die holes, respectively, and length corresponding substantially to the axial length of the counter-bores, press-fitting said inserts into the counter-bores until their inner ends engage the shoulders thereby to effect partial securement of said inserts in their counter-bores, and upsetting the material of the die member over the outer ends of the inserts in manner as to positively yet detachably secure them against movement axially from their counter-bores.

9. The method of pelleting die construction substantially as set forth in claim 8, wherein said inserts have the form of longitudinally split sleeves which are initially slightly oversize with respect to the diameter of the counter-bores, and wherein the step of pressing said inserts into the counter-bores elfects limited contraction of the inserts and a corresponding frictional securement thereof to the wall surfaces of the counterbores.

References Cited in the file of this patent UNITED STATES PATENTS 1,952,025 Witte a Mar. 20, 1934 2,l38,404 Haas Nov. 29, 1938 2,598,975 Coulter June 3, 1952 2,902,949 Meakin Sept. 8, 1959 FOREIGN PATENTS 309,301 Germany Nov. 16, 1918 

